PIK3CA and breast cancer: As for the progress of related signaling pathways in the treatment of HER2-positive breast cancer, the clinical research on overcoming trastuzumab resistance through the PI3K inhibitor alpelisib has made progress to a certain extent, a phase III clinical trial is ongoing evaluating alpelisib in combination with trastuzumab for patients with HER2-positive MBC and PI3K mutations(NCT04208178).